Imaging device

ABSTRACT

When color correction is performed on a particular color of a video signal, in order to change a color correction amount according to image-taking circumstances or capture video images without influencing colors not to be corrected, image-taking mode information containing information on particular colors determined according to predetermined image-taking conditions is set. There are provided selection means for selecting desired image-taking mode information from the image-taking mode information, and storage means for storing color convergence parameter values containing position data indicative of a position of a predetermined color in a color-difference plane, correction range setting data for setting to a correction range a predetermined range centered at the position of the predetermined color, and convergence coefficient data for converging a particular color corresponding to the correction range to the position indicative of the predetermined color. Color convergence parameter values for the corresponding particular color from the storage means is selected and set on the basis of the selected image-taking mode information, and a particular color in a video signal is corrected into the predetermined color on the basis of a correction amount calculated on the basis of the set color convergence parameter values.

TECHNICAL FIELD

The present invention relates to an image capture apparatus and, morespecifically, to an image capture apparatus which is capable ofcorrecting a particular color in a video signal into a predeterminedcolor such as a memory color.

BACKGROUND ART

In the prior art, there exists an apparatus such as a digital cameracapable of automatically performing various settings such as focus andwhite balance and correcting a particular color in a video signal into apredetermined color appropriate for a scene where an image is to betaken, by selecting an image-taking mode (for example, a sea, a nightview, a portrait and a landscape) according to the scene where the imageis to be taken.

In addition, in the field of such apparatus capable of correcting aparticular color in a video signal, there has been invented an imageprocessing device or the like which corrects a particular color into acolor, which humans latently memorize and feel to be the most beautiful,i.e., a so-called memory color. (For example, refer to Japanese PatentApplication Publication Number 2001-292390 (Pages 3-5, FIG. 5)).

In such apparatus, for example, when a user takes an image of alandscape containing a blue sky, the blue color (particular color) ofthe actually taken image is corrected into a blue color based on amemory color, because when the user views the taken image, the userusually imagines a more vivid blue color than the color of the blue skythat the user actually viewed.

The present applicant has also filed an image capture apparatus which iscapable of extracting from a captured video signal a video signal of aparticular color to be corrected, calculating a correction amount forthe color on the extracted video signal of the particular color, andcorrecting the particular color to be corrected, on the basis of thecalculated correction amount (Patent Application Number 2003-88060).

An operation outline of the color correction processing of the imagecapture apparatus filed by the present applicant will be describedbelow.

FIG. 8 is a block diagram showing a schematic configuration of essentialsections for performing color signal correction processing in the imagecapture apparatus, which is provided with an image capture lens section101A, an image capture device 102A, a S/H (Sample/Hold) circuit 103A, anAGC (Automatic Gain Control) circuit 104A, an A/D (Analog/Digital)conversion circuit 105A, a particular-color extraction circuit 106A, aWB (White Balance) circuit 107A, a gamma correction circuit 108A, asignal processing circuit 109A, a color-difference signal correctioncircuit 110A, an image-taking mode selection circuit 120A, a colorcorrection value setting circuit 130A, and the like.

First, when an image-taking mode is selected by the image-taking modeselection circuit 120A, the particular-color extraction circuit 106Aextracts particular-color signals (Rs[red]/Gs[green]/Bs[blue]) which arevideo signals of a particular color, from video signals(R[red]/G[green]/B[blue]) on the basis of image-taking mode informationcorresponding to the image-taking mode, and the particular-color signalsare corrected for white balance and grayscale by a WB circuit 141A and agamma correction circuit 142A of a particular-color signal processingsection 140A and are converted into a luminance signal Ys and acolor-difference signal [Bs−Ys] and a color-difference signal [Rs−Ys] bya signal processing circuit 143A.

Then, a color-difference signal processing circuit 144A of theparticular-color signal processing section 140A performs detection ofcolor-difference data from the color-difference signals [Bs−Ys] and[Rs−Ys] transmitted from the signal processing circuit 143A, andtransmits the detected color-difference data to the color correctionvalue setting circuit 130A.

Then, the color correction value setting circuit 130A identifies theparticular color to be corrected, on the basis of the image-taking modeinformation from the image-taking mode selection circuit 120A, readscorrection reference data for the particular color from a look-up table,and calculates a color correction value for correcting the particularcolor into a predetermined color (such as a memory color), on the basisof the read correction reference data for the particular color and thecolor-difference data transmitted from the color-difference signalprocessing circuit 144A.

Then, the color-difference signal correction circuit 110A corrects theparticular color of the video signals (R[red]/G[green]/B [blue]) intothe predetermined color (such as a memory color) on the basis of thecolor correction value calculated by the color correction value settingcircuit 130A.

In this manner, the particular color of the video signals iscolor-corrected into the predetermined color (such as a memory color)according to the image-taking mode so that a video image is reproducedin a color which agrees with the expectation of a user.

However, the above-mentioned image capture apparatus has the problemthat when the particular color of the video signals(R[red]/G[green]/B[blue]) is corrected into the particular color (suchas a memory color) by the color-difference signal correction circuit110A, an influence is exerted on a different color which exists in thesame quadrant as the particular color to be corrected, in acolor-difference plane (two-dimensional coordinates which arerepresented by a vertical axis indicative of a color difference [R−Y]and a horizontal axis indicative of a color difference [B−Y] that is tosay, a color not to be corrected.

Accordingly, a problem to be solved is to provide an image captureapparatus capable of changing, when a particular color of video signalsis to be color-corrected, a color correction amount according to animage taking situation or a video image to be taken, without influencinga color not to be corrected.

DISCLOSURE OF THE INVENTION

To solve the above-mentioned problems, an image capture apparatusaccording to the present invention is configured as follows.

(1) An image capture apparatus including: image-taking mode selectionmeans in which image-taking mode information containing information onparticular colors determined according to predetermined image-takingconditions is set, and which selects desired image-taking modeinformation from the set image-taking mode information; colorconvergence parameter storage means which stores color convergenceparameter values which contain position data indicative of a position ofa predetermined color in a color-difference plane, correction rangesetting data for setting to a correction range a predetermined rangecentered at the position of the predetermined color, and convergencecoefficient data for converging a particular color corresponding to thecorrection range to the position indicative of the predetermined color;color convergence parameter setting means which selects and sets colorconvergence parameter values for the corresponding particular color fromthe color convergence parameter storage means on the basis of theimage-taking mode information selected by the image-taking modeselection means; and color convergence correction processing means whichcorrects a particular color in a video signal into the predeterminedcolor on the basis of a correction amount calculated on the basis of thecolor convergence parameter values set by the color convergenceparameter setting means.

(2) The image capture apparatus described in (1), characterized in thatthe correction range setting data of the color convergence parameterstorage means is data for setting to the correction range a circular orelliptical range centered at the position of the predetermined color inthe color-difference plane.

(3) The image capture apparatus described in (1), characterized in thatthe color convergence parameter storage means is provided with afunction which changes the color convergence parameter values.

(4) The image capture apparatus described in (1), characterized in thatthe image-taking mode selection means is provided with a function whichautomatically selects the image-taking mode information according toimage-taking environments.

(5) An image capture apparatus including: image-taking mode selectionmeans in which image-taking mode information containing information onparticular colors determined according to predetermined image-takingconditions is set, and which selects desired image-taking modeinformation from the set image-taking mode information; colorconvergence parameter storage means which stores color convergenceparameter values which contain position data indicative of a position ofa predetermined color in a color-difference plane, correction rangesetting data for setting to a correction range a predetermined rangecentered at the position of the predetermined color, and convergencecoefficient data for converging a particular color corresponding to thecorrection range to the position indicative of the predetermined color,color convergence parameter setting means which selects and sets colorconvergence parameter values for the corresponding particular color fromthe color convergence parameter storage means on the basis of theimage-taking mode information selected by the image-taking modeselection means; particular-color extraction means which extracts avideo signal of a particular color from a video signal on the basis ofthe image-taking information selected by the image-taking mode selectionmeans; luminance correction means which corrects a luminance level ofthe video signal according to a luminance level in the video signal ofthe particular color extracted by the particular-color extraction means;and color convergence correction processing means which corrects theparticular color in the video signal into the predetermined color on thebasis of a correction amount calculated on the basis of the colorconvergence parameter values set by the color convergence parametersetting means.

(6) The image capture apparatus described in (5), characterized in thatthe luminance correction means calculates a proportion of the videosignal of the particular color in the video signal and corrects theluminance level of the video signal of the particular color according tothe calculated proportion.

(7) The image capture apparatus described in (5), characterized in thatthe correction range setting data of the color convergence parameterstorage means is data for setting to the correction range a circular orelliptical range centered at the position of the predetermined color inthe color-difference plane.

(8) The image capture apparatus described in (5), characterized in thatthe color convergence parameter storage means is provided with afunction which changes the color convergence parameter values.

(9) The image capture apparatus described in (5), characterized in thatthe image-taking mode selection means is provided with a function whichautomatically selects the image-taking mode information according toimage-taking environments.

(10) The image capture method including:

an image-taking mode selection step of selecting desired image-takingmode information from image-taking mode information in whichimage-taking mode information containing information on particularcolors determined according to predetermined image-taking conditions isset;

a particular-color extraction step of extracting a video signal of aparticular color from a video signal on the basis of the image-takingmode information selected in the image-taking mode selection step;

a color-difference detection step of detecting color-difference data onthe particular color from the video signal of the particular colorextracted in the particular-color extraction step;

a color correction value calculation step of selecting correctionreference data on the corresponding particular color from correctionreference data storage means which stores correction reference datawhich is a reference for correcting the particular color into apredetermined color, on the basis of the image-taking mode informationselected in the image-taking mode selection step, and calculating acolor correction value for correcting the corresponding particular colorinto the predetermined color on the basis of the selected correctionreference data and the color-difference data on the particular colordetected by the color-difference detection step; and

a color correction processing step of correcting the particular color ofthe video signal into the predetermined color on the basis of the colorcorrection value calculated in the color correction value calculationstep.

In the image capture apparatus having the above-mentioned configuration,color convergence parameter values for a corresponding particular colorfrom the color convergence parameter means are selected and set on thebasis of selected image-taking mode information. Then, a correctionamount necessary to converge the corresponding particular color to aposition of a particular color (such as a memory color) in acolor-difference plane is calculated on the basis of the colorconvergence parameter values, and a particular color in a video signalis corrected into the particular color (such as a memory color)according to the calculated correction amount. Accordingly, it ispossible to correct the particular color with the correction amountcorresponding to image-taking environments or a captured video image,without influencing colors not to be corrected.

In addition, since the luminance level of a video signal is correctedaccording to a luminance level in a video signal of a particular coloror since the proportion of the video signal of the particular color inthe video signal is calculated and the luminance of the particular coloris corrected according to the calculated proportion, it is possible tocorrect the particular color of the corresponding particular coloraccording to image-taking environments or a captured video image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing a configuration ofessential sections for performing color correction processing in animage pickup apparatus according to the present invention.

FIG. 2 is an explanatory view for explaining correction target ranges ofparticular colors in a color-difference plane.

FIGS. 3A and 3B are explanatory views for explaining circular andelliptical correction target ranges shown in FIG. 2.

FIG. 4A is an explanatory view for explaining a method of calculating adirect distance s from center-point coordinates (xc, yc) in thecorrection target range shown in FIG. 2.

FIG. 5 is a graph showing a relationship between the direct distance sfrom center-point coordinates (xc, yc), a convergence coefficient γ, anda gain amount gain(s, γ).

FIG. 6 is an explanatory view showing one example of a data tableprovided in the image capture apparatus shown in FIG. 1.

FIG. 7 is a flowchart showing a process of color correction processingin the image capture apparatus shown in FIG. 1. FIG. 8 is a blockdiagram schematically showing a configuration of essential sections forcolor correction processing in a prior art image capture apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of an image pickup apparatus according to the presentinvention will be described below with reference to the accompanyingdrawings. However, the drawings are referred to by way of illustrationonly, and are not intended to restrict the technical scope of theinvention.

FIG. 1 is a block diagram showing a schematic configuration of essentialsections for performing color signal correction processing in the imagepickup apparatus. The schematic configuration is provided with an imagecapture lens section 101, an image capture device 102, a S/H(Sample/Hold) circuit 103, an AGC (Automatic Gain Control) circuit 104,an A/D (Analog/Digital) conversion circuit 105, a particular-colorextraction circuit 106, a WB (White Balance) circuit 107, a signalprocessing circuit 108, a color convergence correction circuit 110, aluminance correction circuit 111, an image-taking mode selection circuit120, a color convergence parameter setting circuit 130, aparticular-color signal processing section 140, and the like.

The image capture lens section 101 receives light from an object andtransmits the light to the image capture device 102.

A plurality of pixels which convert light to electrical signals (forexample, in a CCD (Charge Coupled Device)) are arrayed in the imagecapture device 102, and the light from the object which passes throughthe image capture lens section 101 is converted to electrical signals bythe individual pixels and the image capture-device 102 transmits theelectrical signals to the S/H (Sample/Hold) circuit 103 as an analogvideo signal.

The S/H circuit 103 samples the analog video signal transmitted from theimage capture device 102 and transmits sampled values to the AGC circuit104, and holds the sampled values until the processing of the A/Dconversion circuit 105 comes to an end. When this processing comes to anend, the S/H circuit 103 transmits the next sampled values to the AGCcircuit 104.

The AGC circuit 104 amplifies the analog video signal sampled by the S/Hcircuit 103, and transmits the amplified analog video signal to the A/Dconversion circuit 105.

The A/D conversion circuit 105 converts the analog video signalamplified by the AGC circuit 104 to digital video signals(R[red]/G[green]/B[blue]) and transmits the digital video signals to theparticular-color extraction circuit 106 and the WB circuit 107.

The particular-color extraction circuit 106 extracts video signals of aparticular color to be subjected to color correction (hereinafterreferred to as particular-color signals (Rs[red]/Gs[green]/Bs[blue])from the digital video signals (R[red]/G[green]/B[blue]) transmittedfrom the A/D conversion circuit 105, on the basis of image-taking modeinformation from the image-taking mode selection circuit 120 which willbe described later, and calculates a controlled variable of whitebalance and transmits the calculated controlled variable to the WBcircuit 107, and also transmits the extracted particular-color signals(Rs[red]/Gs[green]/Bs[blue]) to a WB circuit 141 of the particular-colorsignal processing section 140.

When the particular-color extraction circuit 106 is to extract the videosignals of the particular color, the particular-color extraction circuit106 changes a particular-color extraction range according to theluminance level of the video signals (R[red]/G[green]/B[blue]) to detectthe video signals of the particular color.

The WB (White Balance) circuit 107 corrects the white balance of thevideo signals (R[red]/G[green]/B[blue]) transmitted from the A/Dconversion circuit 105, in accordance with the controlled variablecalculated by the particular-color extraction circuit, and transmits thecorrected video signal to the signal processing circuit 108.

The signal processing circuit 108 converts the video signals(R[red]/G[green]/B[blue]) transmitted from the WB circuit 107 into aluminance signal Y and a color-difference signal [B−Y] and acolor-difference signal [R−Y]. Then, the signal processing circuit 108transmits the converted color-difference signal [B−Y] and the convertedcolor-difference signal [R−Y] to the color convergence correctioncircuit 110 and also transmits the converted luminance signal Y to theluminance correction circuit 111.

The color convergence correction circuit 110 calculates a correctionamount for correcting the corresponding particular color into apredetermined color (such as a memory color) on the basis of colorconvergence parameter values set by a color convergence parametersetting circuit 130 which will be described later, performs colorconvergence correction processing on the corresponding particular colorin the color-difference signal [B−Y] and the color-difference signal[R−Y] transmitted from the signal processing circuit 108, in accordancewith the calculated correction amount, and transmits a correctedcolor-difference signal [B−Y]” and a corrected color-difference signal[R−Y]” subjected to the color convergence correction procession, to thenext-stage circuit.

The luminance correction circuit 111 corrects the luminance level of theluminance signal Y transmitted from the signal processing circuit 108,on the basis of the image-capture mode information from the image-takingmode selection circuit 120 and the luminance signal Ys of the particularcolor converted by a signal processing circuit 142 of theparticular-color signal processing section 140, and transmits acorrected luminance signal Y″ to the next-stage circuit.

The luminance correction circuit 111 also calculates the proportion ofthe particular color in the entire captured video signals(R[red]/G[green]/B[blue]) (the entire image frame), and corrects theluminance level of the corresponding particular color according to thecalculated proportion.

The image-taking mode selection circuit 120 has a plurality ofimage-taking modes which are set in advance according to image-takingconditions, scenes and the like (such as a sea, a night view, a portraitand a landscape), and is able to select a desired image-taking mode.

When an image taking mode is selected, the image-taking mode selectioncircuit 120 transmits image-taking mode information corresponding to theselected image-taking mode to predetermined sections inside theapparatus, such as the particular-color extraction circuit 106, thecolor convergence parameter setting circuit 130, the luminancecorrection circuit 111, and the like.

The image-taking mode information contains information such asinformation on a particular color to be subjected to color correctiondetermined according to the image-taking mode and the informationnecessary to automatically perform various settings such as focus andwhite balance.

It should be noted that the image-taking mode selection circuit 120 canbe adapted to automatically select an appropriate image-taking modeaccording to image-taking environments such as ambient brightness andthe state of a light source, and can also be adapted to switch betweenautomatic selection and manual selection.

The color convergence parameter setting circuit 130 is provided with adata table in which are stored color correction parameter values forconverging and correcting particular colors into predetermined colorsaccording to the respective image-taking modes, and selects colorconvergence parameter values for the corresponding particular color fromthe data table on the basis of image-taking mode information from theimage-taking mode selection circuit 120 and sets the selected colorconvergence parameter values in the color convergence correction circuit110.

For example, parameter values for color-correcting particular colorsinto colors which humans latently memorize and feel to be the mostbeautiful (hereinafter referred to as memory colors) are stored.

The color convergence parameter values stored in the data table of thecolor convergence parameter setting circuit 130 will be described below.

A position (coordinates) at which a predetermined color to be converged,such as a memory color, exists, in a color-difference plane is fixed,and a color which exists in a predetermined range centered at theposition (coordinates) at which the predetermined color (such as amemory color) exists (hereinafter referred to as a correction targetrange) is a color to be corrected, i.e., a particular color.

The particular color is distributed in a circular or elliptical shapecentered at the predetermined color such as a memory color, so that itis possible to highly accurately correct only a desired particular colorby setting to the correction target range a circular or elliptical rangecentered at the position (coordinates) of the predetermined color (suchas a memory color) in the color-difference plane.

As shown in FIG. 2 by way of example, in a color-difference plane(two-dimensional coordinates represented by a vertical axis indicativeof a color difference [R−Y] and a horizontal axis indicative of a colordifference [B−Y]), a particular color “A” is distributed in a circularrange 10 a centered at a position (coordinates) Ca of a memory color a,a particular color “B” is distributed in a circular range 10 b centeredat a position (coordinates) Cb of a memory color b, a particular color“C”, is distributed in an elliptical range 10 c centered at a position(coordinates) Cc of a memory color c, a particular color “D” isdistributed in an elliptical range 10 d centered at a position(coordinates) Cd of a memory color d, and a particular color “E” isdistributed in a circular range 10 e centered at a position(coordinates) Ce of a memory color e. The respective circular orelliptical ranges corresponding to the memory colors a to e are set tocorrection target ranges 10 a to 10 e.

Each of the circular or elliptical correction target ranges isassociated with the image-taking mode information, and is stored in thedata table as parameter values which respectively indicate thecenter-point coordinates (xc, yc) of the circle or the ellipse, thelengths (a, b) of its major and minor axes, and its inclination(rotational direction) θ, as shown in FIGS. 3A and 3B.

The center-point coordinates (xc, yc) are coordinate data on apredetermined color (such as a memory color) in the color-differenceplane, and are represented by a distance x in the direction of the colordifference [B−Y] from the origin “0” of the color-difference plane and adistance y in the direction of the color difference [R−Y] from theorigin “0” of the color-difference plane. For example, in FIG. 3A, thecenter-point coordinates (xc, yc) are (0, 0), and in FIG. 3B, thecenter-point coordinates (xc, yc) are (x, y).

The lengths (a, b) of the major and minor axes are data indicative ofthe lengths of the diameters of the circle or ellipse in thecolor-difference plane, and as shown in FIG. 3B, the length of thelongest diameter that passes through the center-point coordinates (xc,yc) is represented as the major axis a, while the length of the shortestdiameter that passes through the center-point coordinates (xc, yc) isrepresented as the minor axis b. As shown in FIG. 3A, if the correctiontarget range is a circle, the major and minor axes have the same length(a=b).

The inclination θ is data indicative of the inclination (rotationaldirection) of the ellipse in the color-difference plane as shown in FIG.3B. As shown in FIG. 3A, if the correction target range is a circle, theinclination (rotational direction) θ is zero.

Stored in the data table are not only the parameter values about thecorrection target range (the center-point coordinates (xc, yc), thelengths (a, b) of the major and minor axes, and the inclination θ) butalso a convergence coefficient γ for calculating a correction amount forcorrecting a particular color into the position (coordinates) of apredetermined color (such as a memory color) (hereinafter referred to asa gain amount), i.e., the gain amount for converging the particularcolor to the center-point coordinates (xc, yc).

The convergence coefficient γ is a coefficient value found by evaluatingcolors of various images, and is a coefficient value to be used when thegain amount for converging a particular color in the color-differenceplane into a predetermined color (such as a memory color) on the basisof the following equations 1 and 2.s=√{square root over ((b−y)²+(r−y)² )}  Equation 1

In equation 1, “s”, “b−y” and “r−y” respectively represent: s; a directdistance from the center-point coordinates (xc, yc), b−y; a distance inthe direction of the color difference [B−Y] from the center-pointcoordinates (xc, yc), and r−y; a distance in the direction of the colordifference [R−Y] from center-point coordinates (xc, yc), as shown inFIG. 4.gain(s,γ)=S ^(γ)   Equation 2

In equation 2, s is a direct distance from the center-point coordinates(xc, yc), γ is a convergence coefficient, and gain(s, γ) is a gainamount (correction amount).

FIG. 5 is a normalized graph in which the direct distance s from thecenter-point coordinates (xc, yc) to the power of the convergencecoefficient γ is associated with the gain amount gain(s, γ), and isdivided into “0<γ<1”, “γ=1”, and “γ>1” according to the value of theconvergence coefficient γ.

Thus, the gain amount corresponding to the position (coordinates) of thepredetermined color distributed in the correction target range, i.e.,the gain amount gain(s, γ) corresponding to the distance s, iscalculated by selecting and setting one of convergence coefficients γcorresponding to predetermined colors (such as memory colors).

In addition, the above-mentioned equations 1 and 2 are equations forcalculating the distance s and the gain amount gain(s, γ) when thecorrection target range is a circle, but in the case of the ellipticalcorrection target range shown in FIG. 3B, the transformation ratio atwhich a predetermined circle which is used as a reference is transformedinto the corresponding ellipse is found and the values of the distance sand the gain amount gain(s, γ) of the reference circle are correctedaccording to the transformation ratio.

In this manner, the correction target ranges (the center-pointedcoordinates (xc, yc), the lengths of major axis and minor axis (a, b)and the inclination θ) and the convergence coefficients γ which arerespectively associated with the particular colors set according to therespective image-taking modes are stored in the data table as the colorconvergence parameter values.

FIG. 6 schematically shows one example of the data table. In the row ofan image-taking mode 0, color convergence parameter values such as aparticular color “A”, the center-point coordinates (xc, yc)→(0, 0), thedistance (length) of the major axis a→5, the distance (length) of theminor axis b→5, the inclination θ→“0”, the convergence coefficientγ→“0.3” are stored. In the row of an image-taking mode 1, colorconvergence parameter values such as a particular color “B”, thecenter-point coordinates (xc, yc)→(20, 20), the distance (length) of themajor axis a→3, the distance (length) of the minor axis b→3, theinclination θ→“0”, and the convergence coefficient γ→“0.3” are stored.In the row of an image-taking mode 2, color convergence parameter valuessuch as a particular color C, the center-point coordinates (xc,yc)→(−20, 20), the distance (length) of the major axis a=10, thedistance (length) of the minor axis b→5, the inclination θ→−π/4, and theconvergence coefficient γ→0.3 are stored. In the row of an image-takingmode 3, color convergence parameter values such as a particular color“D”, the center-point coordinates (xc, yc)→(20, −20), the distance(length) of the major axis a→10, the distance (length) of the minor axisb→5, the inclination θ→“−π/4”, and the convergence coefficient γ→“0.3”are stored. In the row of an image-taking mode 4, color convergenceparameter values such as a particular color “E”, the center-pointcoordinates (xc, yc)→(−20, −20), the distance (length) of the major axisa→10, the distance (length) of the minor axis b→5, the inclinationθ→“−3π/4”, and the convergence coefficient γ→“0.3” are stored.

In addition, the color convergence parameter values of the data tablecan be changed. For example, in the case of an apparatus capable ofacquiring data from a recording medium such as a memory card, the colorconvergence parameter values can be changed to different colorconvergence parameter values recorded on the recording medium (such as amemory card), or in the case of an apparatus connectable to acommunication network, the color convergence parameter values can bechanged to color convergence parameter values acquired via thecommunication network. Accordingly, users can change the colorconvergence parameter values to color convergence parameter values whichcan provide colors or hues suited to the preferences of the users, orcan individually customize the color convergence parameter valuesaccording to the users.

The particular-color signal processing section 140 is provided with theWB (White Balance) circuit 141, the signal processing circuit 142 andthe like.

The WB (White Balance) circuit 141 of the particular-color signalprocessing section 140 corrects the white balance of theparticular-color signals, (Rs[red]/Gs[green]/Bs[blue]) extracted by theparticular-color extraction circuit 106 and transmits the correctedparticular-color signals to the signal processing circuit 142.

The signal processing circuit 142 of the particular-color signalprocessing section 140 converts the particular-color signals(Rs[red]/Gs[green]/Bs[blue]) transmitted from the WB circuit 141 into aluminance signal Ys and a color-difference signal [B−Y] and acolor-difference signal [R−Y], and transmits the converted luminancesignal Ys to the luminance correction circuit 111.

The process of color correction processing in an image capture apparatus100 having the above-mentioned configuration will be described belowwith reference to FIG. 7.

First, when a photographer selects a desired image-taking mode via theimage-taking mode selection circuit 120 or an image-taking mode isautomatically selected according to an image-taking environment,image-taking mode information corresponding to the selected image-takingmode is transmitted to predetermined sections inside the apparatus (theparticular-color extraction circuit 106, the color convergence parametersetting circuit 130, the luminance correction circuit 111, and the like)(ST100).

The color convergence parameter setting circuit 130 selects colorconvergence parameter values for the corresponding particular color fromthe data table on the basis of the image-taking mode informationtransmitted from the image-taking mode selection circuit 120, and setsthe selected color convergence parameter values in the color convergencecorrection circuit 110 (ST110).

In addition, in each of the predetermined sections inside the apparatusother than the color convergence parameter setting circuit 130, varioussettings such as focus and white balance are automatically performed onthe basis of the image-taking mode information corresponding to theimage-taking mode.

When image taking is started, light inputted from an object via theimage capture lens section 101 is converted into an electrical signal bythe image capture device 102, and the electrical signal passes throughthe S/H circuit 103 and the AGC circuit 104 and is converted intodigital video signals (R[red]/G[green]/B[blue]) by the A/D conversioncircuit 105. The digital video signals are transmitted to theparticular-color extraction circuit 106 and the WB (White Balance)circuit 107.

The particular-color extraction circuit 106 extracts particular-colorsignals (Rs[red]/Gs[green]/Bs[blue]) from the video signals(R[red]/G[green]/B[blue]) transmitted from the A/D conversion circuit105, on the basis of the image-taking mode information selected by theimage-taking mode selection circuit 120, and calculates a controlledvariable of white balance and transmits the controlled variable to theWB (White Balance) circuit 107, and also transmits the extractedparticular-color signals (Rs[red]/Gs[green]/Bs[blue]) to the WB (WhiteBalance) circuit 141 of the particular-color signal processing section140 (ST120, ST130).

First of all, the processing process of the video signals(R[red]/G[green]/B[blue]) will be described below.

The WB circuit 107 determines color temperatures of the video signals(R[red]/G[green]/B[blue]) transmitted from the A/D conversion circuit105, and corrects the white balance of the video signals(R[red]/G[green]/B[blue]) on the basis of the controlled variable ofwhite balance calculated by the particular-color extraction circuit 106and transmits the corrected video signals to the signal processingcircuit 108 (ST140).

Then, the signal processing circuit 108 converts the video signals(R[red]/G[green]/B[blue]) corrected for white balance into a luminancesignal Y and a color-difference signal [B−Y] and a color-differencesignal [R−Y], and transmits the converted luminance signal Y to theluminance correction circuit 111 and the converted color-differencesignals [B−Y] and the converted color-difference signal [R−Y] to thecolor convergence correction circuit 110 (ST150).

The processing process of the particular-color signals(Rs[red]/Gs[green]/Bs[blue]) which is executed in parallel with theabove-mentioned process of the video signals (R[red]/G[green]/B[blue])will be described below.

The WB circuit 141 of the particular-color signal processing section 140determines color temperatures of the particular-color signals(Rs[red]/Gs[green]/Bs[blue]) extracted by the particular-colorextraction circuit 1066, and corrects the white balance of theparticular-color signals (Rs[red]/Gs[green]/Bs[blue]) and transmits thecorrected particular-color signals to the signal processing circuit 142(ST160).

Then, the signal processing circuit 142 of the particular-color signalprocessing section 140 converts the particular-color signals(Rs[red]/Gs[green]/Bs[blue]) corrected for white balance into aluminance signal Ys and a color-difference signal [Bs−Ys] and acolor-difference signal [Rs−Ys], and transmits the luminance signal Ysto the luminance correction circuit 111 (ST170).

After the processing of the video signals (R[red]/G[green]/B[blue]) andthe particular-color signals (Rs[red]/Gs[green]/Bs[blue]), colorcorrection processing of the particular color is performed by the colorconvergence correction circuit 110 and the luminance correction circuit111.

The color convergence correction circuit 110 calculates a gain amount(correction amount) for correcting the corresponding particular colorinto a predetermined color (such as a memory color) on the basis of thecolor convergence parameter values set by the color convergenceparameter setting circuit 130 and performs color convergence correctionprocessing of the corresponding particular color in the color-differencesignals [B−Y] and [R−Y] transmitted from the signal processing circuit108, on the basis of the calculated gain amount, and transmits thecolor-difference signal [B−Y]” and the color-difference signal [R−Y]”corrected for color convergence to the next-stage circuit (ST180,ST190).

Specifically, first, the color convergence correction circuit 110calculates the gain amount gain(s, γ) by the above-mentioned equations 1and 2 on the basis of the color convergence parameter values (thecenter-point coordinates (xc, yc), the lengths (a, b) of the major andminor axes, the inclination θ, and the convergence coefficient γ) set bythe color convergence parameter setting circuit 130.

Then, the color convergence correction circuit 110 performs the colorconvergence correction processing by performing multiplicationprocessing on the calculated gain amount gain(s, γ) and thecolor-difference signals [B−Y] and [R−Y] transmitted from the signalprocessing circuit 108, on the basis of the following equation 3.Namely, the corresponding particular color in the video signals isconverged to the position of the predetermined color (such as a memorycolor) in the color-difference plane.[B−Y]″=gain(s,γ)*[B−Y]   Equation 3[R−Y]″=gain(s,γ)*[R−Y]

In the meantime, the luminance correction circuit 111 corrects theluminance level of the luminance signal Y transmitted from the signalprocessing circuit 108, on the basis of the image-taking modeinformation from the image-taking mode selection circuit 120 and theluminance signal Ys converted by the signal processing circuit 142 ofthe particular-color signal processing section 140, and outputs thecorrected luminance signal Y to the next-stage circuit (ST180, ST190).

The luminance correction circuit 111 is also able to calculate theproportion of the particular color in the entire captured video signals(R[red]/G[green]/B[blue]) (the entire image frame) and change acorrection amount for the luminance level of the particular coloraccording to the calculated proportion.

For example, in an image-taking mode for taking a portrait image, if aflesh color of a person is to be corrected, the proportion occupied inthe entire image (image frame) by the flesh color which is a particularcolor is determined, and if the proportion is larger than apredetermined proportion, the correction amount for the luminance levelof the flesh color is increased, whereas if the proportion is smallerthan the predetermined proportion, the correction amount for theluminance level is decreased.

In this manner, it is possible to correct a color-corrected particularcolor into a far more preferable color by changing the correction amountfor the luminance level of a particular color according to image-takingcircumstances during even the same image-taking mode.

As described hereinabove, the image capture apparatus selects and sets acolor convergence parameter value for a particular color from amongpreviously stored color convergence parameter values, on the basis ofautomatically or manually selected image-taking mode information. In acorrection range set by this color convergence parameter value, theparticular color is distributed in a circular or elliptical shapecentered at a predetermined color such as a memory color, so that acircular or elliptical range centered at the position (coordinates) ofthe particular color (such as a memory color) in a color-differenceplane can be set to a correction range to highly accurately correct onlythe particular color.

When image taking is started, a correction amount necessary to convergethe corresponding particular color to the position of the predeterminedcolor (such as a memory color) in the color-difference plane iscalculated on the basis of the color convergence parameter value, andthe particular color in video signals can be corrected into thepredetermined color (such as a memory color) in accordance with thecalculated correction amount, whereby it is possible to achieve thesuperior advantage of correcting a particular color by a correctionamount corresponding to image-taking circumstances or a captured videoimage, without influencing colors not to be corrected.

In addition, if the proportion occupied by a particular color in theentire captured video signal (the entire image frame) is calculated anda correction amount for the luminance level of the particular color ischanged according to the calculated proportion, it is possible toachieve the superior advantage of correcting the particular color of thecaptured video signal into a luminance which can provide a preferablecolor corresponding to image-taking circumstances or a captured videoimage.

1. An image capture apparatus, comprising: image-taking mode selectionmeans, in which image-taking mode information containing information ona particular color determined according to a predetermined image-takingcondition is set, for selecting desired image-taking mode informationfrom the set image-taking mode information; color convergence parameterstorage means for storing a color convergence parameter value containingposition data indicative of a position of a predetermined color in acolor-difference plane, correction range setting data for setting to acorrection range a predetermined range centered at the position of thepredetermined color, and convergence coefficient data for converging aparticular color corresponding to the correction range to the positionindicative of the predetermined color; color convergence parametersetting means for selecting and setting a color convergence parametervalue for the corresponding particular color from the color convergenceparameter storage means on a basis of the image-taking mode informationselected by the image-taking mode selection means; and color convergencecorrection processing means for correcting a particular color in a videosignal into the predetermined color on a basis of a correction amountcalculated on a basis of the color convergence parameter value set bythe color convergence parameter setting means.
 2. The image captureapparatus according to claim 1, characterized in that the correctionrange setting data of the color convergence parameter storage means isdata for setting to the correction range a circular or elliptical rangecentered at the position of the predetermined color in thecolor-difference plane.
 3. The image capture apparatus according to clam1, characterized in that the color convergence parameter storage meanscomprises a function for changing the color convergence parametervalues.
 4. The image capture apparatus according to clam 1,characterized in that the image-taking mode selection means comprises afunction for automatically selecting the image-taking mode informationaccording to an image-taking environment.
 5. An image capture apparatus,comprising: image-taking mode selection means, in which image-takingmode information containing information on a particular color determinedaccording to a predetermined image-taking condition is set, forselecting desired image-taking mode information from the setimage-taking mode information; color convergence parameter storage meansfor storing a color convergence parameter value containing position dataindicative of a position of a predetermined color in a color-differenceplane, correction range setting data for setting to a correction range apredetermined range centered at the position of the predetermined color,and convergence coefficient data for converging a particular colorcorresponding to the correction range to the position indicative of thepredetermined color; color convergence parameter setting means forselecting and setting a color convergence parameter value for thecorresponding particular color from the color convergence parameterstorage means on a basis of the image-taking mode information selectedby the image-taking mode selection means; particular-color extractionmeans for extracting a video signal of a particular color from a videosignal on a basis of the image-taking information selected by theimage-taking mode selection means; luminance correction means forcorrecting a luminance level of the video signal according to aluminance level in the video signal of the particular color extracted bythe particular-color extraction means; and color convergence correctionprocessing means for correcting the particular color in the video signalinto the predetermined color on a basis of a correction amountcalculated on a basis of the color convergence parameter value set bythe color convergence parameter setting means.
 6. The image captureapparatus according to claim 5, characterized in that the luminancecorrection means calculates a proportion of the video signal of theparticular color in the video signal and corrects the luminance level ofthe video signal of the particular color according to the calculatedproportion.
 7. The image capture apparatus according to claim 5,characterized in that the correction range setting data of the colorconvergence parameter storage means is data for setting to thecorrection range a circular or elliptical range centered at the positionof the predetermined color in the color-difference plane.
 8. The imagecapture apparatus according to claim 5, characterized in that the colorconvergence parameter storage means comprises a function for changingthe color convergence parameter value.
 9. The image capture apparatusaccording to claim 5, characterized in that the image-taking modeselection means comprises a function for automatically selecting theimage-taking mode information according to an image-taking environment.10. An image capture method, characterized by comprising: animage-taking mode selection step of selecting desired image-taking modeinformation from image-taking mode information in which image-takingmode information containing information on a particular color determinedaccording to a predetermined image-taking condition is set; aparticular-color extraction step of extracting a video signal of aparticular color from a video signal on the basis of the image-takingmode information selected in the image-taking mode selection step; acolor-difference detection step of detecting color-difference data onthe particular color from the video signal of the particular colorextracted in the particular-color extraction step; a color correctionvalue calculation step of selecting correction reference data on thecorresponding particular color from correction reference data storagemeans storing correction reference data which is a reference forcorrecting the particular color into a predetermined color, on a basisof the image-taking mode information selected in the image-taking modeselection step, and calculating a color correction value for correctingthe corresponding particular color into the predetermined color on abasis of the selected correction reference data and the color-differencedata on the particular color detected by the color-difference detectionstep; and a color correction processing step of correcting theparticular color of the video signal into the predetermined color on abasis of the color correction value calculated in the color correctionvalue calculation step.